How drones are being used in agriculture

Drone use in agriculture is growing as more farmers realise the technology’s ability to perform key tasks and its fast-developing potential to take on bigger roles in the future

Figures show the 2.8m sales of drones worldwide are still dominated by private users. But commercial uptake is the main growth area with sales predicted to soar from 174,000 drones in 2017 to 805,000 units in 2021. Within that total, global financial analysts, PricewaterhouseCoopers, estimate agriculture is currently the second largest market for drone use behind construction.

It calculates that drones already contribute $32bn (€26bn) worth of services to farmers across the world.

The appeal of the technology has been further enhanced by declining costs of drone equipment which is reducing initial outlays and offering the potential for a quicker return on investment.

According to leading mechatronics researcher Jonathan Gill, who is based at Harper Adams University in England, it is possible to recover the cost of a high-tech drone in under three years. A previous calculation, carried out by Mr Gill considered a €23,000 (£20,000) camera/drone that took three years to pay back on a 200ha arable area. The payback came through increased yield generated through more precise disease and nitrogen monitoring which was made possible by the camera’s multispectral camera.

Since that calculation was drawn up three years ago costs of the same drone and camera equipment have reduced to about €14,000 (£12,000) making potential return on investment far quicker.  Mr Gill suggests other savings that could help recover the cost of investment include reduced man hours needed for crop checking and lower fuel use for travelling around the farm.

The affordability of the drone and rapid advances in the scope of the technology are fuelling an ever-widening range of current uses. These include aerial mapping, plant health monitoring, weed detection and - where legislation allows - crop spraying.

Current Uses

Precision fertilizer programme planning 
Nitrogen deficient areas in a crop can be clearly identified from above using drones fitted with cameras that have enhanced sensors. The sensors are calibrated to limit the effect of changing sunlight levels and allow a more accurate calculation of the green area to be made.

Flying operations start from the late winter with drones taking hundreds of images of the crop’s developing canopy. The images are then stitched together to form a map and software is used to identify early growth patterns. From there a precise fertilizer programme can be tailored to match the crop’s varying nutrient requirements in different areas of the field.

Weed and disease control programmes 
Using similar techniques to the fertilizer planning, drone operators can accurately assess weed and disease levels in arable crops. The drone gathers data that identifies the differing reflective properties of various plant species and areas of the crop which have succumbed to disease. When this information is allied to software and analyzed, weed species and disease can be pinpointed and targeted with high precision crop control measures. Orchards can also make use of the technology with accurate identification and tagging of trees infected with a range of diseases.

Tree and land mapping 
As well as the disease control aspect, orchard fruit growers can benefit from reports on tree and row spacing with accurate calculations of canopy coverage. The same applies to forestry and timber production where drones can play an important role in accessing remote sites on terrain that would otherwise be difficult to cover.

The ability to cover large ground areas is a major benefit for mapping generally. Hundreds of hectares can be mapped in a day with the most sophisticated systems accurately pinpointing changes in terrain and boundary features to within 10cm. The data captured then creates a 3D computer model to highlight ground features and any changes that may have occurred.

The information can be used to give area measurements for administration purposes or fed into machinery software to help the operator avoid hazards such as electric cables, flooded areas, changes in water courses, or drainage hardware. The drone has a significant advantage over a more time-consuming ground-based system which would involve travelling to, and moving around, the sites and logging GPS co-ordinates.
 
Crop Spraying 
Larger drones are already capable of applying small quantities of pesticide or fertilizer to crops, orchards and forested areas. However, only a handful of regions and countries permit the use of drones for this type of task. Since September 2016 farmers in Queensland, Australia, were granted permission to apply pesticides from drones, joining farmers in the USA, Switzerland, New Zealand and China.

The main legislative barriers are bans on aerial spraying which were implemented due to environmental concerns and counter terrorism laws that broadly prevent drones from carrying payloads. Work is underway in numerous countries to amend rules to allow spraying to go ahead because of the potential benefits which include:
- Zero ground compaction
- Spraying taller crops (maize)
- Access to difficult terrain
- Spraying under or around power lines pylons
- Spot spraying of small diseased areas or pest populations
- Lower cost in time, wasted product and fuel
- Reduced environmental risks as areas are small

One country which has led aerial spraying using drones is China. The drones used are approximately 2m in diameter, weigh about 20kg and can carry a 10-litre payload to treat about 1ha/hr. Active radar systems and real time knowledge (RTK) gps are programmed into the drone which then flies a pre-set route at location accuracies down to 1cm. The forward and downward looking radar systems allow the drone to keep a consistently low height above the crop, minimising the chance of spray drift. Sophisticated object avoidance software also means the drone can navigate around obstructions.

The Future

Drone swarms 
While most spraying is carried out using single drone units to either patch, strip or spot spray, rapidly developing technology within the drone may allow much larger areas to be sprayed in the future. Drones are already capable of communicating with each other to avoid collisions and to fly in formation. This could allow a string or swarm of drones to apply pesticide across whole fields in the future. While trials are under way, the main obstacle to success could lie in legislation with governments and military officials wary of terrorist threat presented by a swarm of unmanned aircraft. 

Plant Pollination 
A decline in bee numbers has prompted worldwide concern over the future of plant pollination which underpins horticultural and agricultural production. In Japan, researchers have investigated the use of drones to carry out the task. Measuring just four centimetres across and weighing only 15 grams, the drone has proved it is capable of pollinating flowers without damaging the plant. The research team is now progressing with an auto-piloted version that could be unleashed by the grower to carry out the work on its own.

Beyond Visual Line Of Sight (BVLOS) flying 
A common component of drone legislation is a safety restriction, limiting maximum operating distances to 500m. Within that distance the pilot must also have Visual Line Of Sight at all times. However, pilots claim that these rules are severely limiting the technology’s potential. For example, if a field boundary being mapped is more than 500m distant, or undulating fields or trees block the line of sight, the operator must gather up equipment and move.

Operators and manufacturers are pressing the case for these restrictions to be lifted. They argue that BVLOS flying would be a game-changer for the drone industry and that it is safe because of developments in on-board safety technology. Sense-and-avoid systems, remote viewing using imaging devices and pre-programmed return-to-base measures, which are triggered if the drone loses contact, all mean drones can be safely operated in rural areas. Further testing of this technology is taking place with the aim of proving that BVLOS flying could be safe and become a reality in the near future.